In a fluid filling machine that fills a container such as a plastic bottle with a fluid such as drink, the fill amount of a fluid is sensed by an electromagnetic flow meter that measures the flow rate based on an electromotive force generated in the fluid to which a magnetic field has been applied (see cited documents 1 to 4, for example).
Some of such fluid filling machines have the function of filling different containers with different fluids. In such fluid filling machines, filling of a fluid is stopped once in preparation work for changing the type of a filling fluid or adjusting the filling operation.
FIG. 7 is an explanatory diagram illustrating changes in the state of an electromagnetic flow meter in preparation work, FIG. 7(a) illustrates a liquid exchange process, and FIG. 7(b) illustrates an adjustment process.
In the liquid exchange process in FIG. 7(a), the old fluid previously used is first drained and, after the old fluid is drained completely, a new fluid is preliminarily flowed. After a certain amount of the new liquid is preliminarily flowed, the process reaches the fill waiting state of new fluid. Accordingly, in such a liquid exchange process, the fluid state in the detector of the electromagnetic flow meter is the full-water state at the start of draining, the non-full-water state at the completion of draining, and the full-water state again when the new liquid is preliminarily flowed.
In addition, the adjustment process in FIG. 7(b) first starts a trial filling for filling the container with a fluid on a trial base in the fill waiting state, reaches fill completion through a filling state, checks the fill amount and the like, and returns to the fill waiting state. Accordingly, in such an adjustment process, the fluid state in the detector of the electromagnetic flow meter remains to be the full-water state from the fill waiting state to the fill waiting state which follows trial fill start and fill completion. The full-water state in the electromagnetic flow meter indicates a state in which the fluid to be measured makes contact with the electrodes provided on the inner wall of the flow path of the detector.